Viral hepatitis

• Viral Hepatitis


  Several diseases of the liver, collectively known as hepatitis, are caused by a wide range of virus families

  
• Hepatitis viruses


  • Hepatitis A
  • Hepatitis B
  • Hepatitis C
  • Hepatitis Delta
  • Hepatitis E

  
• Hepatitis A virus (HAV)

  • Genus: Hepatovirus, Family: Picornaviridae
  • RNA virus with positive polarity
  • Non-enveloped, 27nm diameter

  
• Hepatitis B virus (HBV)


  • Genus: Orthohepadnavirus, Family: Hepadnaviridae
  • Partially double-stranded DNA virus
  • Enveloped, 40nm diameter

  
• Hepatitis C virus (HCV)

  • Family: Flaviviridae
  • RNA virus with positive polarity
  • Enveloped, 30-60nm diameter

  
• Hepatitis Delta virus (HDV)

  • RNA virus with negative polarity
  • Enveloped, ~40nm diameter

  
• Hepatitis E virus (HEV)

  • Family: Hepeviridae (previously in Caliciviridae)
  • RNA virus with positive polarity
  • Non-enveloped, 30-35nm diameter

  
• Hepatitis A occurs sporadically and in epidemics worldwide, with a tendency for cyclic recurrences

  
• Hepatitis A virus is one of the most frequent causes of foodborne infection

  
• Hepatitis A viruses persist in the environment and can withstand food production processes routinely used to inactivate or control bacterial pathogens

  
• Globally, around 1.4 million symptomatic cases of hepatitis A occur each year, and about 114 million infections (symptomatic and asymptomatic)

  
• Acute hepatitis A resulted in 11,200 deaths in 2015 globally

  
• WHO estimates that in 2016, 7134 persons died from hepatitis A worldwide (accounting for 0.5% of the mortality due to viral hepatitis)

  
• Hepatitis B virus can survive outside the body for at least 7 days and remain infectious

  
• WHO estimates 296 million people were living with chronic hepatitis B infection in 2019, with 1.5 million new infections each year

  
• In 2019, hepatitis B resulted in an estimated 820,000 deaths, mostly from cirrhosis and hepatocellular carcinoma

  
• About 20 to 30% of those chronically infected with hepatitis B develop cirrhosis and/or liver cancer

  
• HBV/HIV Coinfection


  About 1% of persons living with HBV infection (2.7 million people) are also infected with HIV<|>Tenofovir, included in HIV treatment, is also active against HBV
• Serological markers


  HBsAg, HBcAg, HBeAg - induce corresponding antibodies<|>Anti-HBs indicates recovery and protection<|>Anti-HBe indicates low infectivity<|>Anti-HBc indicates past or current infection
• In chronic carriers, patient fails to form anti-HBs and appearance of anti-HBe may delay
• Although HBsAg persists in the blood for many years, liver function is normal, the patient is well and can infect others without knowing it

  
• Anti-HBe


  Presence indicates little or no infectivity
• Anti-HBc


  Indicates a past or current infection, and therefore, cannot be used to differentiate between acute and chronic infection
• With the exception of HBcAg (which does not circulate in the blood), all these antigens and antibodies, together with the viral DNA polymerase, can be detected in the blood at various times after infection and are referred to as 'markers', because their presence or absence in an individual patient mark the course of the disease and also give a good idea of the degree of infectivity for others

  
• Hepatitis B is not curable but it is treatable

  
• There is no specific treatment for acute hepatitis B

  
• Chronic hepatitis B is treated with interferon-alpha, lamivudine, or adefovir

  
• WHO recommends the use of oral treatments - tenofovir or entecavir, because these are the most potent drugs to suppress hepatitis B virus

  
• In most people, however, the treatment does not cure hepatitis B infection, but only suppress the viral replication

  
• Therefore, most people who start hepatitis B treatment must continue for life
• HBV can be prevented by safe and effective vaccine
• Active immunization against HBV is achieved with a recombinant HBsAg vaccine
• Passive immunization with HBV immune globulin is given to neonates born to HBsAg (+) mothers and after needlestick exposures
• Liver transplantation is sometimes used in people with cirrhosis or liver cancer in high-income countries, with varying success
• Hepatitis C virus (Hepacivirus)

  In the family Flaviviridae (of which yellow fever is the prototype)

  
• HCV, like HBV, is mostly transmitted by exposure to blood and blood products, accidental injections during medical procedures, and injection drug use. Sexual and maternal-foetal transmission is less common
• WHO estimates that about 170 million people, or 3 per cent of the world's population, are infected with HCV
• Approximately 700 000 people die each year from hepatitis C-related liver diseases
• Flaviviruses


  • Icosahedral, positive strand RNA envelope viruses
  • The virus particle is about 30-60nm across
  • The viral envelope proteins are glycoprotein spikes
  • The protein core is the major component of the nucleocapsid. This may inhibit host response and is thought to bind to viral RNA during assembly

  
• HCV infect hepatocytes


  Liver injury mediated by cytotoxic T cells that contribute both to inflammation and viral clearance